The handheld engine operating machines sold on the market are made to be capable of operate optimally in a shipping condition after the process of being adjusted so as to correct individual, parts deviations in carburetor and engine in the factory where the operating machines are manufactured.
Regardless of that adjustment, an optimum combustion of fuel in an engine is changed according to the effect of temperature, atmospheric pressure, type of fuel, brake-in of an engine, clogging of an air cleaner, and the like in using environment. In the result it often happens that it is impossible for the engine to maintain an optimum operating state, which brings about disadvantages such as an increase in fuel consumption, reduction in engine power output, and an increase in exhaust gas emission.
As means for resolving these disadvantages, it is recommended that an operator adjust a fuel needle valve of a carburetor to control fuel in an optimum combust ion for each operation. However, high-level skill and specialised equipment are required for this adjustment.
As a conventional art for accurately and automatically carrying out adjustment of a carburetor, capable of responding adequately to changes in the using environment, for example, the method for operating internal combustion engine is disclosed in Patent Document (Japan Publication No. 2011-012685). In this conventional art, it is possible to accurately adjust an amount of fuel supply, and an engine rotational speed depends on a composition of fuel-air mixture, being adjusted in accordance with an operating curve. This is, the conventional art comprises, in order to set a desired composition of fuel-air mixture, a step of changing operating parameters (a composition of fuel-air mixture) until an operating point is positioned at a desired portion.